Ferromagnetic Ordering in the Layer‐Structured Pd(HS2O7)2

The reaction of (NO₂)(CF₃SO₃) and elemental palladium in oleum (65 % SO₃) leads to violet single crystals of Pd(HS₂O₇)₂ (monoclinic, P2₁/c, Z=2, a=927.80(9), b=682.58(7), c=920.84(9) pm, β=117.756(2)°, wR₂=0.0439). In the crystal structure, the Pd²⁺ ions show an uncommon octahedral coordination of six oxygen atoms belonging to six HS₂O₇^? ions. The linkage of [PdO₆] octahedra and the hydrogendisulfate anions leads to a layer structure, and the layers are held together by hydrogen bonds. The unusual coordination of the Pd²⁺ ions results in an electronic d⁸ high‐spin configuration, which leads to the paramagnetic behavior of the compound. Moreover, at low temperature, a ferromagnetic ordering was observed with a Curie temperature of 8 K.